In a tractor having an engine mounted on a foremost portion of the vehicle body, a hydraulic pump for supplying fluid to one or more fluid-operated devices disposed at a rear end portion of the vehicle body, such as a hydraulic lift cylinder, is generally disposed at a foremost portion of the vehicle body so that it can be driven directly by the engine as shown, for example, in JP, U No. 58-39320. On the other hand, fluid or oil to be fed to such a pump is reserved within the vehicle body such that the inlet of a fluid suction path for the pump is located within a rear portion of the vehicle body so that, even when the tractor is climbing up a slope, the suction inlet is immersed in oil whereby failure in the suction of fluid or oil is not caused. One example of such arrangement of the fluid suction path is shown in the above-referenced Japanese publication. According to this arrangement of a hydraulic pump and a fluid suction path therefor, both of the suction path and a fluid supply path from the pump to the fluid-operated device are large in length.
Accordingly, there is known, as shown in JP, A No. 63-20237 and in JP, A No. 6-191303, a prior art in which a transmission shaft, constantly driven by engine, is provided within the vehicle body such that it extends to an axial mid location of the vehicle body where a PTO-clutch is disposed for connecting the transmission shaft to a rear power take-off shaft, and in which a hydraulic pump of the above-referenced function is mounted on an outer surface of a side wall of the vehicle body such that driving power therefore is taken off from the transmission shaft at a location just before the PTO-clutch.
This structure will greatly reduce the length of a fluid suction path for the pump and that of a fluid supply path from the pump to a fluid-operated device disposed at a rear portion of the vehicle body, as compared to the structure in which a hydraulic pump is disposed at a foremost location of the vehicle body. However, fluid suction and supply paths of a considerably large length are still required. Further, the arrangement of a pump on an outer side surface of the vehicle body at an axial mid portion thereof will prevent a step for use in riding the tractor from being arranged at a low level. Because linkage means and other connecting or operating means are concentratedly arranged in proximity to an outer surface of the vehicle body, the pump must be arranged such that it does not cause an interference with such linkage means etc. Further, such linkage means will make inspection or maintenance of the pump difficult.
In a tractor having a power take-off shaft projecting outwardly from a rear housing of the vehicle body, there is known from, for example, JP, Y2 No. 63-23222 to provide a PTO-brake which is operable to brake the power take-off shaft in the disengaged condition of a PTO-clutch for selectively transmitting power to the take-off shaft. In the tractor shown in the above-referenced Japanese publication, the PTO-clutch is fashioned into a fluid-operated clutch and the PTO-brake is associated with this fluid-operated PTO-clutch such that the operation of PTO-brake is controlled by a single-acting hydraulic cylinder to which fluid pressure for operating the clutch is applied. When the PTO-clutch is placed in the disengaged condition, fluid pressure applied to the single-acting cylinder is released and the PTO-brake is actuated by a biasing force of a spring whereby an inertial rotation of the power take-off shaft is stopped quickly. The PTO-brake is further operable to prevent a rotation of the power take-off shaft can be caused in the disengaged condition of the PTO-clutch due to a drag effect of fluid in the clutch. The single-acting hydraulic cylinder is disposed in a side wall of the tractor rear housing such that it projects outwardly from an outer surface of the side wall.
The structure according to this prior art requires to arrange the single-acting cylinder at a relatively rear location so that it does not interfere with a rear axle housing secured to an outer surface of the side wall and with linkage means disposed thereabout. Thus, the PTO-brake and the PTO-clutch to be braked by it are disposed at a relatively rear location within the rear housing. The rear end of the vehicle body is positioned rearwards correspondingly and the interval between the center axis of rear wheel axles and the rear end of the vehicle body is relatively enlarged. Such a relatively large interval will unbalance the ditribution of weight in an axial direction of the vehicle body particularly when an auxiliary implement of a large weight, such as a rotary tiller, is connected to the rear of the vehicle body. In order to improve the balance, there is a need of attaching a relatively large counterweight to the front of the vehicle body.
In the power take-off assembly shown in the above-referenced JP, Y2 No. 63-23222, there are further provided a speed change mechanism disposed between the PTO-clutch and the power take-off shaft and an interlock mechanism for locking the change mechanism in the engaged condition of PTO-clutch. The interlock mechanism comprises a fluid-acutuated locking member disposed within a thicked wall portion of the tractor rear housing where one end of a slidable fork shaft is supported. Here again, fluid pressure for operating the PTO-clutch is used such that this locking member is actuated to lockingly engage the fork shaft when the PTO-clutch is placed in its engaged condition. For this, a lengthy fluid passage is formed in the wall of the tractor rear housing for conducting clutch-operating fluid to the thickened wall portion.
An object of the present invention is to provide a novel power take-off assembly for tractors which is easily assembled into a tractor and which permits taking-off power for driving a hydraulic pump, pest-controlling implememt or other auxiliary implement disposed at an axial end portion of the vehicle body to a space where a power take-off member does not cause an interference with other components.
A related object is to provide a power take-off assembly in which a pump for hydraulically operating one or more fluid-operated devices disposed at an axial end portion of the vehicle body is arranged at a suitable location.
Another object of the present invention is to provide a power take-off assembly which further includes a PTO-clutch for selectively transmitting power to a power take-off shaft projecting axially outwardly from the vehicle body, and which is easily assembled into a tractor.
A further object of the invention is to provide a power take-off assembly in which a PTO-brake for braking the power take-off shaft in the disengaged condition of PTO-clutch is provided in a way in which balance as to the distribution of weight in the axial direction of the vehicle body is improved.
A still further object of the invention is to provide a power take-off assembly in which a speed change mechanism is disposed between the PTO-clutch and the power take-off shaft and in which an interlock mechanism for locking the speed change mechanism in the engaged condition of PTO-clutch is provided in a simple way.